Inkjet image forming method

ABSTRACT

There is disclosed an inkjet image forming method. The method includes recording an image on a recording medium by an inkjet method; supplying a liquid including powder particles having a volume-average particle diameter of 1 μm or more to a surface of a heating roller; and applying the powder particles onto the recording medium via the heating roller.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on and claims priority under 35 USC 119 fromJapanese Patent Application Nos. 2010-082286 filed on Mar. 31, 2010, and2011-038275 filed on Feb. 24, 2011, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an inkjet image forming method.

2. Description of the Related Art

Printed articles obtained by printing by a commercial printer such asoffset printing, are stacked in large numbers at a high speed in a paperejection section. In this case, the ink (image) printed (recorded) onone printed article is adhered to another stacked printed article, and,if the adhered printed articles are taken apart, a phenomenon (blocking)in which the ink is peeled off from the one printed article and attachedto the another printed article occurs. To suppress this blocking, inoffset printing, inter-ink adhesion is prevented by, after printing,spraying powder such as starch as a blocking suppression agent andattaching the powder to the surface of the printed article.

However, there are cases in which an excessive amount of the powder issprayed. An excessive amount of the powder not only adversely affectsthe printed articles, but also makes a large amount of the powderscatter extensively in the air, thereby intruding into the inside of,for example, a printer, a CTP plate setter, a computer, or a postprocessing machine. As a result, for example, lowering of operationaccuracy and malfunctions are liable to occur, which is not preferable.

Therefore, Japanese Patent Application Laid-Open (JP-A) No. 10-130621suggests a method in which a small amount of powder is sprayed on thesurface of a printed article.

Meanwhile, JP-A No. 2003-39645 discloses a method including a process inwhich an image is recorded on a recording medium by an inkjet method anda process in which a microcapsule-containing liquid is sprayed on therecorded image and the microcapsule is crushed.

SUMMARY OF THE INVENTION

However, in JP-A No. 10-130621, particularly in the case of employingthe method in an inkjet system, if the powder is present in the air evenwhen a small amount of the powder has been sprayed, the powder isattached to the tip of an inkjet nozzle, which easily causes nozzleclogging, and therefore, the powder-spraying method cannot be employed.

JP-A No. 2003-39645 discloses a method for improving, for example,weather resistance and water resistance by spraying the microcapsulesonto the image surface and breaking the microcapsules, thereby applyinga film of a core substance having a releasing property (for example,carnauba wax) on the surface of the image, and it is difficult tosuppress blocking by this method. In addition, the above method in whichthe film of the core substance having releasing property is applied isspecifically disclosed only for the inkjet method.

The present invention aims at providing an image forming method withwhich the blocking of recording media on which an image has beenrecorded is suppressed while occurrence of inkjet nozzle clogging isalso suppressed, when employing a mode in which a image is recorded on arecording medium by an inkjet method.

According to an aspect of the present invention, an inkjet image formingmethod is provided. The method includes recording an image on arecording medium by an inkjet method; supplying a liquid includingpowder particles having a volume-average particle diameter of 1 μm ormore to a surface of a heating roller; and applying the powder particlesonto the recording medium via the heating roller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an apparatus for the applicationprocess according to the present invention.

FIG. 2 is a schematic diagram of an apparatus for the image formingmethod according to the present invention.

DETAILED DESCRIPTION

The inkjet image forming method according to the present inventionincludes recording an image on a recording medium by an inkjet method(recording process); and supplying a liquid including powder particlesto the surface of a heating roller, and applying the powder particlesonto the recording medium via the heating roller (application process).Hereinafter, each process is described.

1. Recording Process

In the recording process of the present invention, images are recordedon a recording medium by an inkjet method.

Inkjet Method

The inkjet method is not particularly limited, and may be any knownmethod such as a charge-control method in which an ink is ejected byelectrostatic attraction force; a drop-on-demand method (pressure-pulsemethod) in which a pressure of oscillation of a piezo element isutilized; an acoustic inkjet method in which an ink is ejected byradiation pressure generated by irradiation of ink with acoustic beamsthat have been converted from electric signals; and a thermal inkjetmethod in which an ink is ejected by a pressure generated by formationof bubbles caused by heating of ink (BUBBLEJET, registered trademark).

Examples of the inkjet method include a method in which a large numberof small-volume droplets of an ink having a low concentration, which iscalled a photo ink, are ejected; a method in which inks havingsubstantially the same hue but at different concentrations are used toimprove image quality; and a method in which a clear and colorless inkis used.

The inkjet head used in an inkjet method may be either an on-demand typehead or a continuous type head. Examples of ejection systems includeelectromechanical transduction systems (such as a single-cavity system,a double-cavity system, a vendor system, a piston system, a share-modesystem and a shared-wall system), electrothermal transduction systems(such as a thermal inkjet system and a BUBBLE-JET (registered trademark)system), electrostatic suction systems (such as anelectric-field-control system and a slit-jet system), and dischargesystems (such as a spark jet system), and any of these ejection systemsis applicable.

The ink nozzles and the like used for the inkjet recording are notparticularly limited, and may be selected as appropriate according topurposes.

Regarding the inkjet head, there are (i) a shuttle system in whichrecording is performed while a short serial head having a small lengthis moved in the width direction of a recording medium in a scanningmanner, and (ii) a line system in which a line head having recordingdevices that are aligned to correspond to the entire length of one sideof a recording medium is used. In the line system, image recording canbe performed over the whole of one surface of a recording medium bymoving the recording medium in a direction orthogonal to the directionalong which the recording devices are aligned, and a conveyance system,such as carriage, which moves the short head in a scanning manner isunnecessary. Since a complicated scan-movement control of the movementof the carriage and the recording medium is unnecessary and only therecording medium is moved, the recording speed can be increased comparedto the shuttle system. The inkjet recording method of the invention canbe applied to both of these systems; effects in improving the ejectionaccuracy and scratch resistance of an image are larger when the imageforming method of the invention is applied to a line system, in whichdummy ejection is generally not performed.

The ink amount per droplet ejected from the inkjet head is preferablyfrom 0.5 pl to 15 pl, more preferably from 1 pl to 12 pl, and still morepreferably from 2 pl to 10 pl, from the viewpoint of obtaining a highresolution image.

Recording Medium

According to the inkjet method of the invention, an image is recorded ona recording medium.

The recording medium is not particularly limited, and may be acellulose-based general printing paper, such as high-quality paper, coatpaper, or art paper, that is used for general offset printing and thelike.

The recording medium may be a commercially-available product, andexamples thereof include high-quality papers (A) such as PRINCE WOODFREE (tradename) manufactured by Oji Paper Co., Ltd., SHIRAOI(tradename) manufactured by Nippon Paper Industries Co., Ltd., and NewNPI jo-shitsu (New NPI high-quality; tradename) manufactured by NipponPaper Industries Co., Ltd.; very light-weight coated papers such as EVERLIGHT COATED (tradename) manufactured by Oji Paper Co., Ltd. and AURORAS (tradename) manufactured by Nippon Paper Industries Co., Ltd.;lightweight coat papers (A3) such as TOPKOTE (L) (tradename)manufactured by Oji Paper Co., Ltd. and AURORA L (tradename)manufactured by Nippon Paper Industries Co., Ltd.; coat papers (A2, B2)such as TOPKOTE PLUS (tradename) manufactured by Oji Paper Co., Ltd. andAURORA COAT (tradename) manufactured by Nippon Paper Industries Co.,Ltd.; and art papers (A1) such as 2/SIDE GOLDEN CASK GLOSS (tradename)manufactured by Oji Paper Co., Ltd. and TOKUBISHI ART (tradename)manufactured by Mitsubishi Paper Mills Ltd. As the recording medium,various inkjet-recording papers exclusively for photos may be used.

Among the recording media, coated paper, which is used for generaloffset printing, is preferable. The coated paper is produced generallyby coating a surface of cellulose-based paper (such as high-qualitypaper or neutral paper) that has not been subjected to surfacetreatment, with a coating material so as to form a coating layer. Inparticular, it is preferable to use a coated paper having base paper anda coated layer including kaolin and/or calcium bicarbonate.Specifically, art paper, coat paper, lightweight coat paper, or verylight-weight coated paper is preferable.

Ink Composition

An ink composition used for the present invention is not limited as longas it contains a colorant and water, and a well-known or commerciallyavailable one may be used.

Colorant

As the colorant, for example, a well-known dye and pigment may be usedwith no particular limitation. Among them, from the viewpoints of theink coloring property, a colorant which is almost water-insoluble orpoorly water-soluble is preferable. Specific examples thereof includepigments, dispersive dyes, oil-soluble dyes, coloring matters formingJ-aggregates, and, of these, pigments are more preferable. In thepresent invention, a water-insoluble pigment or a pigmentsurface-treated by a dispersant can be used as the colorant.

The pigment in the present invention is not particularly limited interms of type, and known organic and inorganic pigments may be used.Examples of the pigment include polycyclic pigments, such as an azolake, an azo pigment, a phthalocyanine pigment, a perylene pigment, aperynone pigment, an anthraquinone pigment, a quinacridone pigment, adioxazine pigment, a diketopyrolopyrrole pigment, a thioindigo pigment,an isoindolinone pigment, and a quinophthalone pigment; dye lakes, suchas a basic dye-type lake and an acidic dye-type lake, or organicpigments, such as a nitro pigment, a nitroso pigment, aniline black, anddaylight fluorescent pigments; and inorganic pigments, such as titaniumoxide, iron oxide-based inorganic pigments, and carbon black-basedinorganic pigments. In addition, any pigments can be used as long asthey can be dispersed in an aqueous phase, even if not described in theColor Index. Furthermore, the above pigments surface-treated with, forexample, a surfactant or a polymer dispersant, or a grafted carbon canalso be used. Among the above pigments, more preferable examples of thepigment includes azo pigments, phthalocyanine pigments, anthraquinonepigments, quinacridone pigments, and carbon black-based pigments.

Specific examples of the organic pigments used in the present inventionare shown in the below. With respect to the following colorants, onekind may be used alone, or two or more kinds may be used in combination.

Examples of the organic pigments for orange or yellow include C.I.pigment orange 31, C.I. pigment orange 43, C.I. pigment yellow 12, C.I.pigment yellow 13, C.I. pigment yellow 14, C.I. pigment yellow 15, C.I.pigment yellow 17, C.I. pigment yellow 74, C.I. pigment yellow 93, C.I.pigment yellow 94, C.I. pigment yellow 128, C.I. pigment yellow 138,C.I. pigment yellow 151, C.I. pigment yellow 155, C.I. pigment yellow180, and C.I. pigment yellow 185.

Examples of the organic pigments for magenta or red include C.I. pigmentred 2, C.I. pigment red 3, C.I. pigment red 5, C.I. pigment red 6, C.I.pigment red 7, C.I. pigment red 15, C.I. pigment red 16, C.I. pigmentred 48:1, C.I. pigment red 53:1, C.I. pigment red 57:1, C.I. pigment red122, C.I. pigment red 123, C.I. pigment red 139, C.I. pigment red 144,C.I. pigment red 149, C.I. pigment red 166, C.I. pigment red 177, C.I.pigment red 178, C.I. pigment red 222, and C.I. pigment violet 19.

Examples of the organic pigments for green or cyan include C.I. pigmentblue 15, C.I. pigment blue 15:2, C.I. pigment blue 15:3, C.I. pigmentblue 15:4, C.I. pigment blue 16, C.I. pigment blue 60, C.I. pigmentgreen 7, and siloxane-bridged aluminum phthalocyanine described in thespecification of U.S. Pat. No. 4,311,775.

Examples of the organic pigments for black include C.I. pigment black 1,C.I. pigment black 6, and C.I. pigment black 7.

In a case in which the coloring material in the present invention is apigment, the coloring material may be dispersed in a water-based solventby a dispersant. The dispersant may be a polymer dispersant or a lowmolecular-weight surfactant-type dispersant. The polymer dispersant maybe any of a water-soluble dispersant and a water-insoluble dispersant.

As the water-soluble dispersant of the polymer dispersant in the presentinvention, a hydrophilic polymer compound can be used, and examples ofnatural hydrophilic polymers include vegetal polymers, such as gumarabic, gum tragan, guar gum, karaya gum, locust bean gum,arabinogalacton, pectin, and quince seed starch; sea weed polymers, suchas alginic acid, carrageenen, and agar; animal polymers, such asgelatin, casein, albumin, and collagen; and microorganism polymers, suchas xanthan gum and dextran.

In addition, examples of chemically-modified hydrophilic polymercompound formed from a natural product as a raw material includecellulose polymers, such as methyl cellulose, ethyl cellulose,hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethylcellulose; starch polymers, such as sodium starch glycolate and sodiumstarch phosphate; and sea weed polymers, such as propylene glycolalginate.

Furthermore, examples of synthetic water-soluble polymer compoundsinclude vinyl polymers, such as polyvinyl alcohol, polyvinylpyrrolidone, and polyvinyl methyl ether; acrylic resins, such aspolyacrylamide, polyacrylic acid or an alkali metal salt thereof, andwater-soluble styrene acrylic acid resin, water-soluble styrene maleicacid resin, water-soluble vinyl naphthalene acrylic resin, water-solublevinyl naphthalene malein acid resin, polyvinylpyrrolidone,polyvinylalcohol, alkali metal salts of β-naphthalenesulfonic acidformalin condensate, and polymer compounds having at the side chainsthereof a salt of cationic functional group, such as quaternary ammoniumor amino group.

As the water-insoluble dispersant of the polymer dispersant, a polymerhaving both a hydrophobic portion and a hydrophilic portion can be used,and examples thereof include styrene-(meth)acrylic acid copolymer,styrene-(meth)acrylic acid-(meth)acrylic acid ester copolymer,(meth)acrylic acid ester-(meth)acrylic acid copolymer, polyethyleneglycol (meth)acrylate-(meth)acrylic acid copolymer, and styrene-maleicacid copolymer.

From the viewpoints of a good aggregating property when the treatmentliquid comes into contact, the acid value of the polymer dispersant ispreferably 100 mgKOH/g or less. Furthermore, the acid value is morepreferably from 25 mgKOH/g to 100 mgKOH/g, and particularly preferablyfrom 30 mgKOH/g to 90 mgKOH/g.

The average particle diameter of the colorant is preferably from 10 nmto 200 nm, more preferably from 10 nm to 150 nm, and still morepreferably from 10 nm to 100 nm. If the average particle diameter is 200nm or less, color reproducibility becomes more favorable, and dropletejection property becomes more favorable when ejecting droplets by aninkjet method, and if the average particle diameter is 10 nm or more,light-fastness becomes more favorable. In addition, the particle sizedistribution of the colorant is not particularly limited, and may haveany of wide distribution or mono-dispersed distribution. In addition,two or more kinds of colorants having a mono-dispersed distribution maybe mixed and used.

From the viewpoints of image density, the content of the colorant in theink composition is preferably from 1% by mass to 25% by mass, and morepreferably from 2% by mass to 20% by mass, with respect to the inkcomposition.

Polymer Particles

The ink composition according to the present invention preferablyincludes polymer particles optionally. This can further improve, forexample, the scratch resistance and fixability of images.

Examples of the polymer particles in the present invention includeparticles of resin having anionic groups, and specific examples of theresin include thermoplastic, thermosetting, or modified acryl-based,epoxy-based, polyurethane-based, polyether-based, polyamide-based,unsaturated polyester-based, phenol-based, silicone-based, orfluorine-containing resins; polyvinyl-based resin, such as vinylchloride, vinyl acetate, polyvinyl alcohol, and polyvinyl butyral;polyester-based resin, such as alkyd resin and phthalic resin;amino-based materials, such as melamine resin, melamine-formaldehyderesin, aminonalkyd co-condensate resin, and urea resin; and co-polymersor mixtures thereof. Among them, anionic acryl-based resin can beobtained by polymerizing, for example, an acryl monomer having ananionic group (anionic group-containing acryl monomer) and, optionally,another monomer that can be copolymerized with the anionicgroup-containing acryl monomer in a solvent. Examples of the anionicgroup-containing acryl monomer include acryl monomers having one or moreselected from the group consisting of a carboxy group, a sulfonic acidgroup, and a phosphonic acid group, and, among them, preferable examplesof the anionic group-containing acryl monomer include acryl monomershaving a carboxy group (for example, acrylic acid, methacrylic acid,crotonic acid, ethacrylic acid, propylacrylic acid, isopropylacrylicacid, itaconic acid, and fumaric acid), and more preferable examples ofthe anionic group-containing acryl monomer include acrylic acid andmethacrylic acid. With respect to the polymer particles, one kind may beused alone, or two or more kinds may be used as a mixture.

The molecular weight range of the polymer particles in the presentinvention is, in terms of the weight-average molecular weight,preferably from 3,000 to 200,000, more preferably from 5,000 to 150,000,and still more preferably from 10,000 to 100,000. The weight-averagemolecular weight is measured by gel permeation chromatography (based onpolystyrene-conversion).

The average particle diameter of the polymer particles is, in terms ofthe volume-average particle diameter, preferably in a range from 10 nmto 400 nm, more preferably in a range from 10 nm to 200 nm, still morepreferably in a range from 10 nm to 100 nm, and particularly preferablyin a range of from 10 nm to 50 nm. When the volume-average particlediameter is within the above range, for example, production suitabilityand storage stability may be improved. The average particle diameter ofthe polymer particles is obtained by measuring the volume-averageparticle diameter by a dynamic light scattering method using a NANOTRACparticle size distribution measuring device UPA-EX150 (trade name,manufactured by Nikkiso Co., Ltd.).

From the viewpoints of, for example, the glossiness of images, thecontent of the polymer particles in a liquid composition is preferablyfrom 1% by mass to 30% by mass, and more preferably from 3% by mass to20% by mass, with respect to the ink composition.

Water

The ink composition includes water, and the amount of water is notparticularly limited. However, the content of water is preferably from10% by mass to 99% by mass, more preferably from 30% by mass to 80% bymass, and still more preferably from 50% by mass to 70% by mass.

Organic Solvent

The ink composition may optionally include a water-soluble organicsolvent in addition to water. Preferable examples of a water-solubleorganic solvent include, from the viewpoints of the ejection property,alkyleneoxy alcohols. Furthermore, the ink composition furtherpreferably includes two or more kinds of water-soluble organic solventsincluding at least one kind of alkyleneoxy alcohol and at least one kindof alkyleneoxy ether.

The alkyleneoxy alcohol is preferably propyleneoxy alcohol, and examplesof the propyleneoxy alcohol include SUNNIX GP 250 and SUNNIX GP 400(trade names, all manufactured by Sanyo Chemical Industries Ltd.).

Preferable examples of the alkyleneoxy alcohol ether include ethyleneoxyalkyl ether, the alkyl portion of which has from 1 to 4 carbon atoms orpropyleneoxy alkyl ether the alkyl portion of which has from 1 to 4carbon atoms. Examples of the alkyleneoxy alkyl ether include ethyleneglycol monomethyl ether, ethylene glycol monoethyl ether, ethyleneglycol monobutyl ether, diethylene glycol monomethyl ether, diethyleneglycol monobutyl ether, propylene glycol monomethyl ether, propyleneglycol monobutyl ether, dipropylene glycol monomethyl ether, triethyleneglycol monomethyl ether, ethylene glycol diacetate, ethylene glycolmonomethyl ether acetate, triethylene glycol monomethyl ether,triethylene glycol monoethyl ether, and ethylene glycol monophenylether.

Furthermore, in addition to the above hydrophilic organic solvent, theink composition may optionally include one or more other organicsolvents for the purposes of, for example, drying prevention, permeationacceleration, and viscosity adjustment.

Other Additives

In addition to the above components, the ink composition may optionallyinclude one or more other additives. Examples of such other additivesinclude known additives, such as a polymerizable compound that ispolymerized by active energy rays, a polymerization initiator, ananti-fading agent, an emulsification stabilizer, a permeationaccelerating agent, an ultraviolet absorbent, an antiseptic agent, anantifungal agent, a pH adjuster, a surface tension controller, adefoamer, a viscosity adjuster, a wax, a dispersion stabilizer, ananticorrosive agent, and a chelating agent. Any of theses otheradditives may be directly added after the preparation of the inkcomposition or during the preparation of the ink composition.

2. Application Process

In the application process of the present invention, the liquidincluding powder particles is supplied to the surface of the heatingroller, and the powder particles are applied to the recording medium viathe heating roller. Hereinafter, the liquid including powder particlesmay also be referred to as a “powder-particle containing liquid”.

The powder particle-containing liquid includes powder particles and aliquid (hereinafter, may also be referred to as “first liquid”). Thepowder particle-containing liquid may optionally include one or moreadditional components.

The first liquid may be any liquid that can disperse the powderparticles, but, in the present invention, the powder-particle containingliquid preferably includes a nonvolatile solvent as the first liquid.When a nonvolatile solvent is used in the powder particle-containingliquid, the coating property of the powder particle-containing liquidcan be improved. The nonvolatile solvent in the present invention refersto a solvent which does not boil at 150° C. or less at 1 atmosphere.Examples of such a solvent include silicone oils or fluorine-containingoils, such as dimethyl silicone oil, fluorinated oil, fluorosiliconeoil, and amino-modified silicone oil; and liquid paraffin. Among them,from the viewpoints of forming a uniform release agent layer on thesurface layer of the heating roller and easily transferring the powderparticles to the surface of a recorded image, silicone oil orfluorine-containing oil is preferable.

Examples of these liquids include dimethyl silicone oils, such as“KF-96-10cs,” “KF-96-20cs”, “KF-96-30cs,” “KF-96-50cs,” “KF-96-100cs,”“KF-96-200cs,” “KF-96-300cs,” “KF-96-500cs,” “KF-96-1000cs,”“KF-96-3000cs,” “KF-96-5000cs,” “KF-96-10000cs” (trade names, allmanufactured by Shin-Etsu Chemical Co., Ltd.), “SH200-10CS,”“SH200-100CS,” “SH200-1000CS,” and “SH200-10000CS” (trade names, allmanufactured by Dow Corning Toray Corporation);

Amino-modified silicone oils, such as “KF-393,” “KF-859,” “KF-860,”“KF-861,” “KF-864,” “KF-865,” “KF-867,” “KF-868,” “KF-869,” “KF-6012,”“KF-880,” “KF-8002,” “KF-8004,” “KF-8005,” “KF-877,” “KF-8008,”“KF-8010,” “KF-8012,” “X-22-3820W,” “X-22-3939A,” “X-22-161A,”“X-22-161B,” “X-22-1660B-3” (trade names, all manufactured by Shin-EtsuChemical Co., Ltd.), “BY16-871,” “BY16-853U,” “FZ-3705,” “SF8417,”“BY16-849,” “FZ-3785,” “BY16-890,” “BY16-208,” “BY16-893,” “FZ-3789,”“BY16-878,” and “BY16-891” (trade names, all manufactured by Dow CorningToray Corporation);

Fluorosilicone oils, such as “FL-5,” “X22-821,” “X-22-822,”“FL-100-100CS,” “FL-100-450CS,” “FL-100-1000CS,” “FL-100-10000CS,”(trade names, all manufactured by Shin-Etsu Chemical Co., Ltd.),“FS1265-300CS,” “FS1265-1000CS,” and “FS1265-10000CS” (trade names, allmanufactured by Dow Corning Toray Corporation).

With respect to the first liquid, one kind may be used singly or two ormore kinds may be used in combination.

The powder particles are not limited as long as they can suppressblocking. The powder particles may be either poorly water-soluble orwater-insoluble, and, in the present invention, water-insoluble powderparticles are preferable. When poorly water-soluble particles orwater-insoluble powder particles, preferably water-insoluble particles,are used as the powder particles, it is possible to effectively preventthe lowering of the blocking suppression effect and the occurrence ofunevenness on the recorded image surface, which are caused by the powderparticles dissolving or permeating into the inside of the recorded imagewhen the powder particles are applied on the recording image. In thepresent invention, the term ‘water-insoluble’ refers to a solubility inwhich an amount of dissolution is 5.0 parts by mass or less with respectto 100 parts by mass of water (25° C.). The powder particle-containingliquid in the present invention, containing the powder particles, ispreferably in a dispersed state, i.e., the powder particle-containingliquid is preferably a powder particle dispersion liquid.

Examples of the powder particles include inorganic particles and organicparticles. Specific examples of the inorganic particles include silica(silicon dioxide), titanium oxide, magnesium oxide, aluminum oxide, andcalcium carbonate. Examples of the organic particles include polymethyl(meth)acrylate, polystyrene, and polyester. Among them, polymethyl(meth)acrylate or silica is preferable. Meanwhile, the polymethyl(meth)acrylate refers to at least one kind of polymethyl acrylate andpolymethyl methacrylate (PMMA).

With respect to the powder particles, one kind may be used alone, or twoor more kinds may be used in combination.

The volume-average particle diameter of the powder particles is 1 μm ormore. This can suppress occurrence of blocking. From the viewpoints ofobtaining a high quality printing sample without changing tactile senseof the printing sample, while attaining sufficient blocking suppressioneffects regardless of the basis weight of the recording medium, thevolume-average particle diameter may be from 1 μm to 40 μm, preferablyabout from 5 μm to 35 μm, and more preferably about from 10 μm to 30 μm.Specifically, in a case where a recording medium having a basis weightof 127 g/m² or higher, such as a thick coat paper or a paper board forpacking, is used, the volume average diameter of the powder particles ispreferably from 10 μm to 30 μmm, from the viewpoint of suppressingstacker blocking

The volume average particle diameter of the powder particles is measuredwith a MICROTRAC particle size distribution analyzer MT-3200 (tradename, available from Nikkiso Co., Ltd.) using a dry cell. There is noparticular restriction on the particle size distribution of the powderparticles, and the powder particles may have a mono-dispersed particlesize distribution or may have a wide particle size distribution. Whenthe ratio of the particles having a preferable particle diameter islarger, the blocking suppression effect may also be larger and,therefore, the powder particles having a mono-dispersed particle sizedistribution are preferably used.

The content of the powder particles included in the powderparticle-containing liquid is not limited, and, for example, withrespect to the total amount of the powder particle-containing liquid,the content may be about from 1% by mass to 50% by mass, and preferablyabout from 5% by mass to 40% by mass.

The surface temperature (heating temperature) of the heating roller isnot limited as long as a film can be formed with the polymer particlesin the ink composition at the surface temperature, but the temperaturemay be, for example, about from 30° C. to 120° C., and preferably aboutfrom 50° C. to 90° C. This can improve the film strength of images.

A heating method is not particularly limited, but preferable examplesthereof include methods of heating in a non-contact manner, such as amethod of heating with a heating element, such as a nichrome wireheater, a method of supplying a warm air or a hot air, and a method ofheating with, for example, a halogen lamp or an infrared ray lamp.

The heating roller may be either a metal roller made of metal or aroller having, at the surface of a core made of metal, a coated layermade of an elastic body and, optionally, a surface layer (also called areleasing, layer). The metal roller and the core made of metal can bemade of, for example, an iron, aluminum, or SUS-made cylindrical body.The coated layer is particularly preferably formed with a silicone resinor fluorine resin having a releasing property. The heating rollerpreferably has a heating element built in the inside of the core metalthereof. When, for example, two rollers are used, one of the two rollersmay have a heating element built in the core metal thereof. Heatingtreatment and pressure-applying treatment may be conducted at the sametime by passing a recording medium between rollers. Two heating rollersmay be used, and heating may be conducted by passing the recordingmedium between the two heating rollers. Preferable examples of theheating element include a halogen lamp heater, a ceramic heater, and anichrome wire.

The powder particles may be supplied to the heating roller by directlyor indirectly attaching the liquid including the powder particles(powder particle-containing liquid) to the heating roller. Examples ofsuch methods include a method in which a fabric material, into which thepowder particle-containing liquid has been impregnated, is brought intocontact with the surface of the heating roller, a method in which thepowder particle-containing liquid is sprayed to the surface of theheating roller, and a method in which the powder particle-containingliquid is coated on the heating roller with a roll coater. Inparticular, the method in which a fabric material is brought intocontact with the heating roller is preferable from the standpoint thatan appropriate amount of the powder particle-containing liquid can besupplied to the roller surface without unevenness. The fabric material(web member) used in this method may be any of woven fabric andnon-woven fabric, and commercially available or known materials may beused, but a heat-resistant nonwoven fabric is preferable since thefabric material is brought into contact with the heating roller.Examples of the heat-resistance nonwoven fabric include polyvinylidenechloride, polyethylene, aramide, polyester, polyamide and the mixturesthereof. The amount of the powder particle-containing liquid impregnatedinto the fabric material is not limited, but may be in a range of aboutfrom 1 g/m² to 100 g/m² (particularly 2 g/m² to 50 g/m²).

In the application process in the present invention, the powderparticles may be applied to the surface of a printed article by, forexample, pressing the heating roller having the powder particlesattached at the roller surface to a recording medium (printed article)on which an image has been recorded. The pressing method is not limited,and examples thereof include (i) a method in which a pressure-applyingroller is additionally used and the recording medium passes between apair of these rollers (heating roller and pressure-applying roller) insuch a manner that the recorded image surface of the recording medium isbrought into contact with the heating roller, (ii) a method in which twoheating rollers are used and a recording medium passes between a pair ofthe heating rollers, (iii) a method in which the printed article, beingconveyed on a conveying belt, passes in such a manner that the recordedimage surface of the recording medium is brought into contact with theheating roller, and (iv) a combination thereof.

The application process of the present invention may include a processof fixing the recorded image (fixing process), before or after theprocess using a heating roller. In general, in the fixing process, it isnecessary to use a fixing roller, which is a fixing member, but, in thepresent invention, the heating roller can serve as the fixing roller aswell as a roller for the application of the powder particles. Therefore,it is possible to conduct the fixation of the recorded image and theapplication of the powder particles at the same time without using aseparate fixing roller; whereby, equipment can be miniaturized.Meanwhile, a method in which the fixation is conducted by further usinga fixing member, such as a separate fixing roller, is also included inthe scope of the present invention.

The pressure for the pressing is not limited, but the pressure ispreferably such a level that the powder particles are not crushed. Assuch a pressure, for example, the pressure is preferably in a range offrom 0.1 MPa to 3.0 MPa, more preferably in a range of from 0.1 MPa to1.0 MPa, and still more preferably in a range of from 0.1 MPa to 0.5MPa.

The nip time of passing a recording medium through the heating roller ispreferably from 1 millisecond to 10 seconds, more preferably from 2milliseconds to 1 second, and still more preferably from 4 millisecondsto 100 milliseconds. The nip width is preferably from 0.1 mm to 100 mm,more preferably from 0.5 mm to 50 mm, and still more preferably from 1mm to 10 mm.

To realize the above pressure (nip pressure), elastic members, such assprings, having a tensile force may be selected and installed at bothends of the rollers, such as the heating roller, so as to obtain adesirable nip pressure in consideration of the nip gap.

A belt substrate for conveying the recording medium is not limited, but,for example, seamless electroformed nickel is preferable, and apreferable thickness of the substrate is from 10 μm to 100 μm. Examplesof materials for the belt substrate further include, other than nickel,aluminum, iron, and polyethylene. In the case of providing a siliconeresin or a fluorine resin, the thickness of the layer formed with such aresin is preferably from 1 μm to 50 μm, and more preferably from 10 μmto 30 μm.

The conveying speed of the recording medium is preferably in a range offrom 200 mm/second to 700 mm/second, more preferably from 300 mm/secondto 650 mm/second, and still more preferably from 400 mm/second to 600mm/second.

The amount of the powder particles applied to the recording medium isnot limited, and can be appropriately adjusted by, for example, theamount supplied to the heating roller and the concentration of thepowder particle-containing liquid. In a method in which a fabricmaterial (web member) into which the powder particle-containing liquidhas been impregnated is used, the amount can be adjusted by, forexample, the amount impregnated into the fabric material and the amountof the fabric material delivered.

In the image forming method according to the present invention, a devicesuch as an ink-drying zone may be provided, whereby drying process maybe conducted between the recording process and the application processor after the application process.

An example of the application process in the present invention isdescribed with reference to FIG. 1 as follows. The fabric material (webmember) 5 into which the powder particle-containing liquid has beenimpregnated is pressed to the heating roller (fixing roller) 1 by theweb-pressing roller 3. The fabric material 5 continuously supplies thepowder particle-containing liquid to the surface of the heating rollerby coming into contact with the heating roller 1 while being wound bythe rotation of the delivery roller 2 and the winding roller 4.

A preferable example of the image forming method according to thepresent invention is described with reference to the schematic diagramof an apparatus shown in FIG. 2. In the apparatus, once the recordingmedium 11 is conveyed to by, for example the conveying belt 10, therecording medium is, first of all, applied with a treatment liquid bythe treatment liquid-coating bar 13 at the treatment liquid-coatingsection 12, and, subsequently, dried by a dryer 15 at the heating anddrying section 14. Then, when the recording medium has arrived at theinkjet recording section 16, the ink composition is ejected from theinkjet nozzle 17 toward the recording medium so as to form a recordedimage on the recording medium. The recording medium (printed article) onwhich the image has been recorded is conveyed through another heatingand drying section 14 to the fixing section. The fixing section isprovided with the heating roller (fixing roller) 1 and thepressure-applying roller 6.

The heating roller has been pressed by the fabric material 5, part ofwhich had been impregnated with the powder particle-containing liquid,consequently, powder particles are attached to the surface of theroller. The conveyed printed article passes between the heating roller 1and the pressure-applying roller 6. By this passing, the image formed onthe recording medium is fixed and the powder particles attached to thesurface of the heating roller are transferred to the surface of theprinted article. After that, the recording medium is optionally cut intoa predetermined size, and is ejected from an ejection outlet, wherebyprinted articles are stacked on an ejection tray (not shown).

Meanwhile, in FIG. 2, the treatment liquid-coating section 12 isprovided and a treatment liquid application process (described below) isconducted on the surface of the recording medium by bringing thetreatment liquid-coating bar into contact with the surface of therecording medium. Furthermore, in FIG. 2, the heating and dryingsections 14 are provided after the treatment liquid-coating section 12and the inkjet-recording section 16, respectively, so as to conduct thedrying processes. However, the treatment liquid application process andheating process are not essential.

—Treatment Liquid Application Process—

The image forming method of the present invention may further include atreatment liquid application process in which the treatment liquid isapplied to a recording medium. In the treatment liquid applicationprocess, the treatment liquid capable of causing formation of anaggregate when contacting with the ink composition is applied to arecording medium, thereby contacting the treatment liquid with the inkcomposition, to form an image. When the treatment liquid contacts withthe ink composition, dispersed particles, such as polymer particles anda colorant (for example, a pigment), in the ink composition aggregate,as a result of which an image is fixed to the recording medium.

The application of the treatment liquid can be performed employing aknown method such as a coating method, an inkjet method, or a dipmethod. The coating method may be a known coating method such as amethod using a bar coater, an extrusion die coater, an air doctorcoater, a blade coater, a rod coater, a knife coater, a squeeze coater,a reverse roll coater, or the like. The specifics of the inkjet methodare as described above.

The treatment liquid application process may be conducted either beforeor after the ink application process (recording process) in which theink composition is used.

In the invention, it is preferable that the recording process isconducted after applying the treatment liquid in the treatment liquidapplication process. That is, it is preferable that the treatment liquidfor aggregating a colorant (preferably a pigment) in the ink compositionis applied onto the recording medium in advance of the application ofthe ink composition, and the ink composition is applied so as to contactwith the treatment liquid that has been applied onto the recordingmedium, thereby forming an image. Inkjet recording at higher speeds canbe realized, and an image having high density and high resolution can beobtained even when high-speed recording is performed.

The amount of the treatment liquid to be applied is not particularlylimited as long as the treatment liquid is capable of causingaggregation when contacting with the ink composition. The amount of thetreatment liquid to be applied is preferably such an amount that theamount of aggregating component (such as a di- or higher-valentcarboxylic acid or a cationic organic compound) is from 0.1 g/m² orhigher. The amount of the treatment liquid is more preferably such thatthe amount of the aggregating component applied is from 0.1 to 1.0 g/m²,still more preferably such that the amount of the aggregating componentapplied is from 0.2 to 0.8 g/m². When the amount of the aggregatingcomponent applied is 0.1 g/m² or higher, the aggregation reactionproceeds favorably. The amount of the aggregating component applied of1.0 g/m² or less is preferable from the viewpoint of glossiness.

The treatment liquid in the invention is capable of causing aggregationwhen contacting with the ink composition as described above.Specifically, the treatment liquid preferably includes an aggregatingcomponent capable of causing formation of an aggregate by aggregatingdispersed particles, such as colorant particles (pigment and the like),contained in the ink composition. The treatment liquid may furtherinclude other components, as necessary. Use of the treatment liquid withthe ink composition realizes inkjet recording at higher speeds, andrealizes formation of an image having high density, high resolution, andexcellent print properties (such as reproduction of thin lines and fineareas) even at high recording speeds.

The treatment liquid may include at least one aggregating componentcapable of causing formation of an aggregate when contacting with theink composition. As a result of the treatment liquid mixing into the inkcomposition ejected by an inkjet method, aggregation of, for example,pigment and the like that have been stably dispersed in the inkcomposition is promoted.

The treatment liquid is, for example, a liquid that is capable ofcausing formation of an aggregate by changing the pH of the inkcomposition. In this case, the pH (at 25° C. ° C.) of the treatmentliquid is preferably from 1 to 6, more preferably from 1.2 to 5, andstill more preferably from 1.5 to 4, from the viewpoint of theaggregation speed of the ink composition. In this case, the pH (at 25°C.) of the ink composition to be ejected is preferably from 7.5 to 9.5,and more preferably from 8.0 to 9.0.

In the invention, it is preferable that the pH (at 25° C.) of the inkcomposition is 7.5 or higher and the pH of the treatment liquid (at 25°C.) is from 1.5 to 3, from the viewpoints of image density, resolution,and inkjet recording at higher speeds.

The aggregating component may be used singly, or two or more thereof maybe used in mixture.

The treatment liquid may include at least one acidic compound as anaggregating component. Examples of acidic compounds that can be usedinclude compounds having a phosphoric acid group, a phosphonic acidgroup, a phosphinic acid group, a sulfuric acid group, a sulfonic acidgroup, a sulfinic acid group, or a carboxyl group, and salts thereof(such as polyvalent metal salts thereof). From the viewpoint ofaggregation speed of the ink composition, compounds having a phosphoricacid group or a carboxyl group are preferable, and compounds having acarboxyl group are more preferable.

The compounds having a carboxyl group are preferably selected frompolyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid,maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid,citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoricacid, pyrrolidonecarboxylic acid, pyronecarboxylic acid,pyrrolecarboxylic acid, furancarboxylic acid, pyridinecarboxylic acid,coumalic acid, thiophenecarboxylic acid, and nicotinic acid, derivativesof these compounds, and salts thereof (such as polyvalent metal saltsthereof).

These compounds may be used singly, or in combination of two or morethereof.

The treatment liquid in the present invention may further include anaqueous solvent (for example, water) in addition to an acidic compound.

The content of the at least one acidic compound in the treatment liquidis preferably from 5% by mass to 95% by mass, more preferably from 10%by mass to 80% by mass, still more preferably from 15% by mass to 50% bymass, and further preferably from 18% by mass to 30% by mass, relativeto the total mass of the treatment liquid, from the viewpoint ofaggregation effect.

The treatment liquid may include, as an aggregating component, apolyvalent metal salt. Use of this treatment liquid improves high-speedaggregation properties. Examples of the polyvalent metal salt include: asalt of an alkaline earth metal, which belongs to Group 2 of thePeriodic Table, such as magnesium or calcium; a salt of a transitionmetal belonging to Group 3 of the Periodic Table, such as lanthanum; asalt of a metal belonging to Group 13 of the Periodic Table, such asaluminum; and a salt of a lanthanide, such as neodymium. The salt ofsuch a metal is preferably a carboxylic acid salt (such as a formate,acetate, or benzoate), a nitrate, a chloride, or a thiocyanate. Inparticular, the following salts are preferable: a calcium or magnesiumsalt of a carboxylic acid (such as formic acid, acetic acid, or benzoicacid); a calcium or magnesium salt of nitric acid; calcium chloride;magnesium chloride; and a calcium or magnesium salt of thiocyanic acid.

The content of polyvalent metal salt in the treatment liquid ispreferably from 1% by mass to 10% by mass, more preferably from 1.5% bymass to 7% by mass, and still more preferably from 2% by mass to 6% bymass, form the viewpoint of aggregation effects.

The treatment liquid may include at least one cationic organic compoundas an aggregating component. Examples of the cationic organic compoundinclude cationic polymers such as a poly(vinylpyridine) salt,poly(alkylaminoethyl acrylate), poly(alkylaminoethyl methacrylate),poly(vinylimidazol), polyethyleneimine, polybiguanide, polyguanide, andpolyallylamine, and derivatives thereof.

The weight average molecular weight of the cationic polymer ispreferably smaller from the viewpoint of the viscosity of the treatmentliquid. When the treatment is applied to a recording medium by an inkjetmethod, the weight average molecular weight of the cationic polymer ispreferably in the range of from 1,000 to 500,000, more preferably from1,500 to 200,000, and still more preferably from 2,000 to 100,000. Aweight average molecular weight of 1000 or more is preferable in termsof aggregation speed, and a weight average molecular weight of 500,000or less is preferable in terms of ejection reliability. The abovepreferable ranges do not apply when the treatment liquid is applied to arecording medium by methods other than inkjet.

The cationic organic compound is preferably, for example, a primary,secondary, or tertiary amine salt-type compound. Examples of the aminesalt-type compound include a cationic amine salt-type compound and anamphoteric surfactant that exhibits cationic properties at a desired pHrange. Examples of the cationic amine salt-type compound include:hydrochloride or acetate of an amine, such as hydrochloride or acetateof laurylamine, cocoamine, stearylamine, rosin amine, or the like; aquaternary ammonium salt compound such as lauryl trimethyl ammoniumchloride, cetyl trimethyl ammonium chloride, lauryl dimethyl benzylammonium chloride, benzyl tributyl ammonium chloride, or benzalkoniumchloride; a pyridinium salt compound such as cetylpyridinium chloride orcetylpyridinium bromide; an imidazoline-based cationic compound such as2-heptadecenyl-hydroxyethyl imidazoline; and an ethyleneoxide adduct ofa higher alkylamine such as dihydroxyethyl stearylamine. Examples of theamphoteric surfactant that exhibits cationic properties at a desired pHrange include: amino acid-type amphoteric surfactant, a carboxylate-typeamphoteric surfactant such as stearyl dimethyl betaine or lauryldihydroxyethyl betaine, a sulfuric ester-type amphoteric surfactant, asulfonic acid-type amphoteric surfactant, and a phosphoric ester-typeamphoteric surfactant.

Among them, a di- or higher valent cationic organic compound ispreferable.

The content of the at least one cationic organic compound in thetreatment liquid is preferably from 1% by mass to 50% by mass, and morepreferably from 2% by mass to 30% by mass, from the viewpoint ofaggregation effects.

Among them, a di- or higher-valent carboxylic acid or a di- orhigher-valent cationic organic compound is preferable as an aggregatingcomponent, from the viewpoints of aggregation properties and scratchresistance of an image.

The viscosity of the treatment liquid is preferably in the range of from1 mPa·s to 30 mPa·s, more preferably from 1 mPa·s to 20 mPa·s, and stillmore preferably from 2 mPa·s to 15 mPa·s, and particularly preferablyfrom 2 mPa·s to 10 mPa·s, from the viewpoint of the aggregation speed ofthe ink composition. Here, the viscosity is measured using a VISCOMETERTV-22 (tradename, manufactured by TOKI SANGYO CO. LTD) at 20° C.

The surface tension of the treatment liquid is preferably from 20 mN/mto 60 mN/m, more preferably from 20 mN/m to 45 mN/m, and still morepreferably from 25 mN/m to 40 mN/m, from the viewpoint of theaggregation speed of the ink composition. Here, the surface tension ismeasured using an automatic surface tensiometer CBVP-Z (tradename,manufactured by Kyowa Interface Science Co., Ltd.) at 25° C.

In general, the treatment liquid of the invention may include awater-soluble organic solvent, in addition to the aggregating component.

The treatment liquid may further include one or more other variousadditives, as long as the effects of the invention are not impaired. Thespecifics of the water-soluble organic solvent are the same as thespecifics of the above-described hydrophilic organic solvent in the inkcomposition.

Examples of other additives include a known additive such as ananti-drying agent (humectant), an anti-fading agent, an emulsificationstabilizer, a permeation accelerator, a UV absorber, an antisepticagent, an antifungal agent, a pH adjuster, a surface tension controller,a, defoamer a viscosity adjuster, a dispersant, a dispersion stabilizer,an antirust agent, or a chelating agent. The additives described asspecific examples of other additives contained in the ink composition inthe above description may be used as other additives in the treatmentliquid.

EXAMPLES

Hereinafter, the present invention is described in detail with examples,but the present invention is not limited to the following examples aslong as it does not depart from the gist thereof. Meanwhile, unlessotherwise described, “parts” are mass-based.

The weight average molecular weights were measured using a gelpermeation chromatography (GPC). The GPC was performed using a GPCinstrument, HLC-8220GPC manufactured by Tosoh Corporation, threeserially-connected columns of TSKGEL SUPER HZM-H, TSKGEL SUPER HZ4000,and TSKGEL SUPER HZ2000 (tradenames, all manufactured by TosohCorporation), and THF (tetrahydrofuran) as an eluent. Regarding the GPCconditions, the sample concentration was 0.45% by mass, the flow ratewas 0.35 ml/min, the sample injection amount was 10 μl, and themeasurement temperature is 40° C. The detection was performed by using arefractive index detector. The calibration curve was determined from thefollowing eight standard samples: TSK STANDARD POLYSTYRENEs of F-40,F-20, F-4, F-1, A-5000, A-2500, A-1000, and n-propylbenzene, allmanufactured by Tosoh Corporation.

The acid values were measured by the method defined by JIS standard (JISK0070: 1992), the disclosure of which is incorporated by referenceherein.

The volume average particle diameters of powder particles were measuredwith a MICROTRAC particle size distribution analyzer MT-3200 (tradename, available from Nikkiso Co., Ltd.).

<Preparation of Ink Composition>

(Composition of Cyan Ink C1)

A cyan ink C1 was prepared to have the following composition.

Cyan pigment (pigment blue 15:3): 4% by mass Acrylic-based dispersant(acid value: 65.2 mgKOH/g, 2% by mass weight-average molecular weight:44600): Acrylic-based polymer particles (weight-average 4% by massmolecular weight: 66000): SUNNIX GP250: 10% by mass  (trade name,manufactured by Sanyo Chemical Industries Ltd., water-soluble organicsolvent) Tripropylene glycol monoethyl ether: 10% by mass  (manufacturedby Wako Pure Chemical Industries Ltd., water-soluble organic solvent)OLFINE E1010 (trade name, manufactured by 1% by mass Nissin ChemicalIndustry Co., Ltd., surfactant): Microcrystalline wax: 2% by mass(manufactured by Nippon Seiro Co., Ltd., HI-MIC 1090, trade name)

Ion-exchange water was added to the above components so as to make 100%by mass.

(Composition of Magenta Ink M1)

A magenta ink M1 was prepared to have the same composition as the cyanink C1 except that the cyan pigment in the composition of the cyan inkC1 was changed to a magenta pigment (pigment red 122) in the same amountas the pigment.

(Composition of Yellow Ink Y1)

A yellow ink Y1 was prepared to have the same composition as the cyanink C1 except that the cyan pigment in the composition of the cyan inkC1 was changed to a yellow pigment (pigment yellow 74) in the sameamount as the pigment.

(Composition of Black Ink K1)

A black ink K1 was prepared to have the same composition as the cyan inkC1 except that the cyan pigment in the composition of the cyan ink C1was changed to a black pigment (carbon black) in the same amount as thepigment.

<Preparation of Treatment Liquid>

A treatment liquid was prepared by mixing each component so as to havethe following composition.

Malonic acid (divalent carboxylic acid, manufactured by 15.0% by massWako Pure Chemical Industries Ltd.) Diethylene glycol monomethyl ether(manufactured by 20.0% by mass Wako Pure Chemical Industries Ltd.)Sodium N-Oleoyl-N-methyl taurine (surfactant)  1.0% by mass Ion-exchangewater 64.0% by mass

The treatment liquid had a viscosity of 2.6 mPa·s, a surface tension of37.3 mN/m, and a pH of 1.6. Meanwhile, the surface tension was measuredat 25° C. by the Wilhelmy method using a platinum plate, using anautomatic surface tensiometer CBVP-Z (trade name, manufactured by KyowaInterface Science Co., Ltd.). The viscosity was measured at 30° C. usinga viscometer TV-22 (trade name, manufactured by Toki Sangyo Co., Ltd.).The pH measurement was performed on the undiluted liquid at 25° C. usinga pH meter WM-50EG (trade name, manufactured by DKK Toa Corporation).

—Web Member 1—

Silicone oil: 85.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) Polymethyl metacrylate (PMMA) particles:15.0% by mass (manufactured by Nippon Shokubai Co., Ltd., “EPOSTAR MA1010,” trade name, volume-average particle diameter: 10 μm)

A powder particle dispersion liquid 1 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 1 was manufactured by impregnating the powder particledispersion liquid 1 into a nonwoven fabric so as to have an impregnatingamount of the dispersion liquid of 30 g/m². The nonwoven fabric used wasa mixed material of polyamide and polyester with a weight of 30 g/m² anda thickness of 0.1 mm.

—Web Member 2—

Silicone oil: 85.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) PMMA particles: 15.0% by mass(manufactured by Soken Chemical & Engineering Co., Ltd., “MX-6,” tradename, volume-average particle diameter: 6 μm)

A powder particle dispersion liquid 2 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 2 was manufactured by impregnating the powder particledispersion liquid 2 into a nonwoven fabric so as to have an impregnatingamount of the dispersion liquid of 30 g/m². The nonwoven fabric used forthis web member is the same as that for the web member 1.

—Web Member 3—

Silicone oil: 85.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) PMMA particles: 15.0% by mass(manufactured by Soken Chemical & Engineering Co., Ltd., “MX-1500,”trade name, volume-average particle diameter 15 μm)

A powder particle dispersion liquid 3 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 3 was manufactured by impregnating the powder particledispersion liquid 3 into a nonwoven fabric so as to have an impregnatingamount of the dispersion liquid of 30 g/m². The nonwoven fabric used forthis web member is the same as that for the web member 1.

—Web Member 4—

Silicone oil: 85.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) Silica particles: 15.0% by mass(manufactured by Cabot Corporation, “CAB-O-SIL TG-820F,” trade name,volume-average particle diameter: 10 μm)

A powder particle dispersion liquid 4 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 4 was manufactured by impregnating the powder particledispersion liquid 4 into a nonwoven fabric so as to have an impregnatingamount of the dispersion liquid of 30 g/m². The nonwoven fabric used forthis web member is the same as that for the web member 1.

—Web Member 5—

Silicone oil 100.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.)

A web member 5 was manufactured by impregnating the above silicone oilinto a nonwoven fabric so as to have an impregnating amount of thedispersion liquid of 30 g/m². The nonwoven fabric used for this webmember is the same as that for the web member 1.

—Web Member 6—

Silicone oil 85.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) PMMA particles 15.0% by mass (manufacturedby Soken Chemical & Engineering Co., Ltd., “MP-1600”, trade name,volume-average particle diameter: 0.8 μm)

A powder particle dispersion liquid 6 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 6 was manufactured by impregnating the powder particledispersion liquid 6 into a nonwoven fabric so as to have an impregnatingamount of the dispersion liquid 30 g/m². The nonwoven fabric used forthis web member is the same as that for the web member 1.

—Web Member 11—

Silicone oil 70.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) PMMA particles 30.0% by mass (manufacturedby Soken Chemical & Engineering Co., Ltd., “CHEMISNOW MX-800”, tradename, volume-average particle diameter: 8 μm)

A powder particle dispersion liquid 11 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 11 was manufactured by impregnating the powder particledispersion liquid 11 into a nonwoven fabric so as to have animpregnating amount of the dispersion liquid 140 g/m². As the nonwovenfabric, KYS-80 (trade name, manufactured by Kureha Ltd.) having a weightof 80 g/m² and a thickness of 0.3 mm was used.

—Web Member 12—

Silicone oil 70.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) Crosslinked polystyrene particles 30.0% bymass (manufactured by Sekisui Kasei Plastics Co., Ltd., “TECHPOLYMERSBX-17”, trade name, volume-average particle diameter: 16 μm)

A powder particle dispersion liquid 12 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 12 was manufactured by impregnating the powder particledispersion liquid 12 into a nonwoven fabric so as to have animpregnating amount of the dispersion liquid 140 g/m². As the nonwovenfabric, KYS-80 (trade name, manufactured by Kureha Ltd.) as describedabove was used.

—Web Member 13—

Silicone oil 70.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) PMMA particles 30.0% by mass (manufacturedby Soken Chemical & Engineering Co., Ltd.,“CHEMISNOW MX-2000”, tradename, volume-average particle diameter: 20 μm)

A powder particle dispersion liquid 13 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 13 was manufactured by impregnating the powder particledispersion liquid 13 into a nonwoven fabric so as to have animpregnating amount of the dispersion liquid 140 g/m². As the nonwovenfabric, KYS-80 (trade name, manufactured by Kureha Ltd.) as describedabove was used.

—Web Member 14—

Silicone oil 70.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) PMMA particles 30.0% by mass (manufacturedby Soken Chemical & Engineering Co., Ltd., “CHEMISNOW MX-3000”, tradename, volume-average particle diameter: 30 μm)

A powder particle dispersion liquid 14 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 14 was manufactured by impregnating the powder particledispersion liquid 14 into a nonwoven fabric so as to have animpregnating amount of the dispersion liquid 140 g/m². As the nonwovenfabric, KYS-80 (trade name, manufactured by Kureha Ltd.) as describedabove was used.

—Web Member 15—

Silicone oil 70.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) Crosslinked poly(methyl methacrylate)particles 30.0% by mass (manufactured by Sekisui Kasei Plastics Co.,Ltd., “TECHPOLYMER MBX-40”, trade name, volume-average particlediameter: 40 μm)

A powder particle dispersion liquid 15 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 15 was manufactured by impregnating the powder particledispersion liquid 15 into a nonwoven fabric so as to have animpregnating amount of the dispersion liquid 140 g/m². As the nonwovenfabric, KYS-80 (trade name, manufactured by Kureha Ltd.) as describedabove was used.

—Web Member 16—

Silicone oil 70.0% by mass (“KF-96-100cs,” trade name, manufactured byShin-Etsu Chemical Co., Ltd.) PMMA particles 30.0% by mass (manufacturedby Soken Chemical & Engineering Co., Ltd., “CHEMISNOW MX-6”, trade name,volume-average particle diameter: 0.6 μm)

A powder particle dispersion liquid 16 was prepared by mixing 1 L of aliquid with the above composition with an emulsification devicemanufactured by Silverson Machines, Inc. at 8000 rpm for 10 minutes. Aweb member 16 was manufactured by impregnating the powder particledispersion liquid 16 into a nonwoven fabric so as to have animpregnating amount of the dispersion liquid 140 g/m². As the nonwovenfabric, KYS-80 (trade name, manufactured by Kureha Ltd.) as describedabove was used.

<Image Recording and Evaluation>

As shown below, images were recorded using the inks C1, M1, Y1 and K1and evaluated in the following manner. The evaluation results are shownin Tables 1 and 2 below.

—Scratch Resistance—

A GELJET GX5000 printer head (trade name, a full-line head manufacturedby Ricoh Company Ltd.) was prepared, and a storage tank linked to theprinter head was refilled with the above-obtained cyan ink C1, magentaink M1, yellow ink Y1, and black ink K1. As a recording medium, aTOKUBISHI ART DOUBLE-SIDED N (trade name, manufactured by MitsubishiPaper Mills Limited, basis weight of 104.7 g/m²) and those described inTable 2 were prepared. Each recording medium was fixed on a stage(conveying belt) movable in a predetermined linear direction at 500mm/second. The recording medium was then coated with the above-obtainedtreatment liquid by a wire bar coater so as to have a thickness of about1.5 μm (equivalent to 0.34 g/m² of maloic acid), and dried at 50° C. for2 seconds immediately after the coating (FIG. 2).

Then, the GELJET GX5000 printer head (trade name, a full-line headmanufactured by Ricoh Company Ltd.) was disposed and fixed in a mannersuch that the direction of the line head in which the nozzles werearranged (primary scanning direction) formed an angle of 75.7 degreeswith respect to a direction perpendicular to the moving direction of thestage (secondary scanning direction), and evaluation samples wereobtained by printing solid images by ejecting the inks in a line methodunder the ejection conditions of an ink droplet amount of 3.5 μL, anejection frequency of 24 kHz, and a resolution of 1200 dpi×600 dpi,while moving the recording medium in the secondary scanning direction ata constant speed. Immediately after printing, the evaluation sampleswere dried at 60° C. for 3 seconds.

Next, using the web members as shown in Tables 1 and 2 for Examples 1 to19 and Comparative Examples 1 to 5 respectively, each of the web membersinstalled as shown in FIG. 2 was brought into contact with a heatingroller, and the powder particles impregnated in the web member weresupplied to a heating roller. Then, the recording medium was subjectedto a fixing treatment at a nip pressure of 0.25 MPa and a nip width of 4mm by passing the recording medium between a pair of rollers (heatingroller and pressure-applying roller) heated to 60° C. In this way,evaluation samples were obtained.

Meanwhile, the roller used as the heating roller (fixing roller) in FIG.2 has an SUS-made cylindrical core having a halogen lamp built in, thesurface of which was coated with a silicone resin.

Each of unprinted recording media as shown in Tables 1 and 2 cut into asize of 10 mm×50 mm was wound around a paperweight (with a weight of 470g and a size of 15 mm×30 mm×120 mm) (the contact area of the unprintedrecording medium and the evaluation sample was 150 mm²), and theabove-manufactured evaluation sample was rubbed with three times backand forth (equivalent to a load of 260 kg/m²). After the rubbing, theprinted surface was visually observed, and evaluation was conductedaccording to the evaluation criteria below.

<Evaluation Criteria>

A: No erasing of the image on the printed surface is visually observed.

B: A little erasing of the image on the printed surface is visuallyobserved, which is practically non-problematic.

C: Erasing of the image on the printed surface is visually observed,which is practically problematic.

—Blocking Evaluation—

A solid image was manufactured in the same manner as for the scratchresistance. Two pieces of the evaluation sample were cut into a size of4 cm×4 cm, and were attached together such that the recorded surfacesface each other and, thereto, a pressure of 2.0 MPa was applied for 30seconds by a press machine. Thereafter, the attached two pieces ofevaluation sample were separated (peeled off). How easily the two piecesof the evaluation sample were peeled off and whether there was a colortransfer after the peeling-off was visually observed, and evaluation wasconducted according to the evaluation criteria below.

<Evaluation Criteria>

A: The two pieces are peeled-off naturally, and no color transferbetween the two pieces of paper is observed.

B: Sticking occurs, and color transfer between the two pieces of paperis somewhat observed.

C: Practically problematic. Sticking is strong, and color transferredbetween the two pieces of paper is observed.

—Offset to Heating Roller—

Printing was conducted in the same manner as the scratch resistanceevaluation except that an ink droplet amount was changed to 7.0 pL inthe formation of the solid image, and the temperatures of the heatingroller and the pressure-applying roller were made to be 70° C.Peeling-off of the image portion due to the transfer of images to theheating roller was visually observed, and evaluation was conductedaccording to the evaluation criteria below.

<Evaluation Criteria>

A: No peeling-off of the image on the printed surface is visuallyobserved.

B: A little peeling-off of the image on the printed surface is visuallyobserved, which is practically non-problematic.

C: Peeling-off of the image on the printed surface is visually observed,which is practically problematic.

TABLE 1 Web Member Particle Evaluation Web Powder diameter ScratchBlock- member particles (μm) resistance ing Offset Example 1 Web PMMA 10A A A member 1 Example 2 Web PMMA 6 A A A member 2 Example 3 Web PMMA 15A A A member 3 Example 4 Web Silica 10 A A A member 4 Compar- Web None —C C C ative member example 1 5 Compar- Web PMMA 0.8 B C C ative memberexample 2 6

TABLE 2 Web Member Recording Medium Particle Basis Evaluation Powderdiameter weight Scratch Web member particles (μm) Type of Paper (g/m²)resistance Blocking Offset Example 5 Web member 11 PMMA 8 TOPKOTE PLUS127 A A A Example 6 Web member 11 PMMA 8 TOPKOTE PLUS 157 A B A Example7 Web member 11 PMMA 8 AIBESUTO 310 A B B Example 8 Web member 12Polystyrene 16 TOPKOTE PLUS 127 A A A Example 9 Web member 12Polystyrene 16 TOPKOTE PLUS 157 A A A Example 10 Web member 12Polystyrene 16 AIBESUTO 310 A A A Example 11 Web member 13 PMMA 20TOPKOTE PLUS 127 A A A Example 12 Web member 13 PMMA 20 TOPKOTE PLUS 157A A A Example 13 Web member 13 PMMA 20 AIBESUTO 310 A A A Example 14 Webmember 14 PMMA 30 TOPKOTE PLUS 127 A A A Example 15 Web member 14 PMMA30 TOPKOTE PLUS 157 A A A Example 16 Web member 14 PMMA 30 AIBESUTO 310A B A Example 17 Web member 15 PMMA 40 TOPKOTE PLUS 127 A B A Example 18Web member 15 PMMA 40 TOPKOTE PLUS 157 A B A Example 19 Web member 15PMMA 40 AIBESUTO 310 A B B Comparative Web member 16 PMMA 0.6 TOPKOTEPLUS 127 B C C Example 3 Comparative Web member 16 PMMA 0.6 TOPKOTE PLUS157 B C C Example 4 Comparative Web member 16 PMMA 0.6 AIBESUTO 310 B CC Example 5 TOPKOTE PLUS (trade name), manufactured by Oji Paper Co.,Ltd. AIBESITO (trade name), manufactured by Nippon Daishowa PaperboardCo., Ltd.

If an inkjet printed article is manufactured by the image forming methodaccording to the present invention, since a liquid including the powderparticles are firstly supplied to a heating roller and then applied to arecording medium, it is possible to suppress scattering of the powderparticles into the air and clogging of an inkjet nozzle caused by thescattering of the powder particles into the air. In addition, as isclear from the results in Tables 1 and 2, it can be understood thatblocking can also be suppressed and scratch resistance is also good.Furthermore, it can be also understood that the image forming methodaccording to the present invention can effectively prevent thepeeling-off of recorded images (suppression of fixing offset) in themoment of the transfer of the powder particles by the heating roller.

According to the present invention, it is possible to suppress theblocking of printed articles while clogging of an inkjet nozzle is alsosuppressed, when recording images on a recording medium by an inkjetmethod. In addition, it is also possible to improve scratch resistance.

Exemplary embodiments of the invention include, but are not limited to,the following.

<1> An inkjet image forming method comprising:

-   -   recording an image on a recording medium by an inkjet method;    -   supplying a liquid comprising powder particles having a        volume-average particle diameter of 1 μm or more to a surface of        a heating roller; and    -   applying the powder particles onto the recording medium via the        heating roller.

<2> The inkjet image forming method according to <1>, wherein the powderparticles are supplied to the heating roller by bringing a fabricmaterial, into which the liquid has been impregnated, into contact withthe surface of the heating roller, and the powder particles are appliedonto the recording medium via the heating roller.

<3> The inkjet image forming method according to <1> or <2>, wherein theliquid is supplied to the surface of the heating roller, and the heatingroller is pressed onto the recording medium.

<4> The inkjet image forming method according to <3>, wherein the liquidis supplied to the surface of the heating roller, and the recordingmedium passes between the heating roller and a pressure-applying roller.

<5> The inkjet image forming method according to any one of <1> to <4>,wherein the powder particles are applied to the recording medium in sucha manner that the powder particles are not crushed.

<6> The inkjet image forming method according to any one of <1> to <5>,wherein the liquid comprises a non-volatile solvent.

<7> The inkjet image forming method according to <6>, wherein thenon-volatile solvent is a silicone oil or a fluorine-containing oil.

<8> The inkjet image forming method according to any one of <1> to <7>,wherein the powder particles are water-insoluble.

<9> The inkjet image forming method according to <8>, wherein the powerparticles are selected from the group consisting of poly(methylacrylate) particles, poly(methyl methacrylate) particles, silicaparticles and mixtures thereof

<10> The inkjet image forming method according to any one of <3> to <9>,wherein the heating roller is pressed onto the surface of the recordingmedium with a pressure in a range of from 0.1 MPa to 3.0 MPa.

All publications, patent applications, and technical standards mentionedin this specification are herein incorporated by reference to the sameextent as if each individual publication, patent application, ortechnical standard was specifically and individually indicated to beincorporated by reference.

What is claimed is:
 1. An inkjet image forming method comprising:recording an image on a recording medium by an inkjet method; supplyinga liquid comprising powder particles having a volume-average particlediameter of 1 μm or more to a surface of a heating roller; and applyingthe powder particles onto the recording medium via the heating roller;wherein the powder particles are supplied to the heating roller bybringing a fabric material, into which the liquid has been impregnated,into contact with the surface of the heating roller, and the powderparticles are applied onto the recording medium via the heating roller.2. The inkjet image forming method according to claim 1, wherein theliquid is supplied to the surface of the heating roller, and the heatingroller is pressed onto the recording medium.
 3. The inkjet image formingmethod according to claim 2, wherein the liquid is supplied to thesurface of the heating roller, and the recording medium passes betweenthe heating roller and a pressure-applying roller.
 4. The inkjet imageforming method according to claim 2, wherein the heating roller ispressed onto the surface of the recording medium with a pressure in arange of from 0.1 MPa to 3.0 MPa.
 5. The inkjet image forming methodaccording to claim 1, wherein the powder particles are applied to therecording medium in such a manner that the powder particles are notcrushed.
 6. The inkjet image forming method according to claim 1,wherein the liquid comprises a non-volatile solvent.
 7. The inkjet imageforming method according to claim 6, wherein the non-volatile solvent isa silicone oil or a fluorine-containing oil.
 8. The inkjet image formingmethod according to claim 1, wherein the powder particles arewater-insoluble.
 9. The inkjet image forming method according to claim8, wherein the power particles are selected from the group consisting ofpoly(methyl acrylate) particles, poly(methyl methacrylate) particles,silica particles and mixtures thereof.